2007 Chevy Tahoe 5.3 oil pressure dash gauge starts at 40 and slowly goes down to 0. Seems to hold steady until engine hits 210 temp and then slowly goes to 0. All trouble shooting below but have confirmed with manual gauge oil pressure is steady at 45 psi at idle and dash reads 0.

so originally the symptom above was present as well as an rather significant oil leak. Assumed they were connected. I did start by replacing oil sending unit to try and get an accurate reading. Had no tick or other strange noise. There was oil on back of engine so decided to remove intake manifold vs the knuckle buster option. Since I hand gone that far I replaced the valley cover gasket while there. Didn’t fix issue. Next I pulled oil pan (4x4) and the pickup tube o-ring was brittle. Since I had gone this far I also pulled and replaced oil pump which came with new pickup tube and o-ring. Reassembled and it did resolve oil leak problem. Same behavior of oil pressure reading. I am reading manual oil pressure using a fitting at the oil filter btw.

Other symptom worth noting, when it goes to 0 it will not turn over. Leave it for an hour, will crank right up. I am assuming there is a safety causing this but doesn’t show on dash (safety light goes out as expected).
looking for help on where to start isolating this without dissembling again. All thoughts welcome.

 

Oftentimes, the oil pressure sender at the rear of the engine, top side, needs to be replaced. There are You Tube videos showing this, and oftentimes there is a cylindrical screen underneath that. But it is cramped back there.

Some remove the entire intake manifold for such job - not easy to do !!!

 

I replaced the sender and the screen. Choose to pull the manifold instead of trying the knuckle buster option which is why I went ahead and did the valley pan gasket as well.

other thoughts?

 

I’m think my next steps will be the following but hoping someone can give me their thoughts-
Pull the new sender unit and manually test oil pressure there and confirm I get accurate stable pressure there vs bottom of engine where I have manually tested already.
if I do, bench test new sensor.
If new sensor tests good, put a new pigtail on the sensor, test voltage output and compare to voltage output where wire enters dash (or run new wire).

thoughts? Thoughts on what the issue would be if manually oil pressure test at sender unit is dropping but oil pressure at the oil filter is not? Hopefully not the case but curious. Also curious if my assumption that the reason the engine won’t crank after oil pressure hits 0 for 20 mins or so is electronic safety related or if someone else could cause this.

 

I did the same thing, replaced the sensor and screen, and the oil pressure sensor picked up the pressure that was needed. About 40PSI for operating temps.

 

ok. So connected oil pressure manual gauge to sending unit port. Oil pressure is normal until engine engine warms up. The it begins to drop and will drop to 0. No codes showing up so assuming no stuck lifter. Thoughts?

 

The gauge in the dash is Not fed directly from the sender . The sender transmits data to the ECM/PCM then the data buss transmits the Perceived Oil Pressure value to the IP (Instrument Panel) control module . the IP control module then displays the value assigned by the ECM . You could have a faulty IPCM and have absolutely nothing wrong with the OP sensor on the engine . Only real way to know is with an expensive Scan and Diagnostic tool that can display the values to each device using Live Stream Data . and can actually read the data packets transmitted on the data buss . Or you can keep using the "Parts Cannon" approach and pray for a positive outcome ... Also remember that " New does NOT equal GOOD"
I have people all the time say that "it's a New part" and I have to remind them that "New does Not = Good"

 

Unless you work in the trade, most folks have no idea that cheap parts from some places just don't measure up.

A dealership cannot afford comebacks so their parts might cost a little more, but we do the job once. There are some good aftermarket parts suppliers and some that market imported junk. It never hurts to check where your part was manufactured, could save some problems.

 

Genuine GM sensors ONLY for no issues.

 

I never posted the solution I realized. My apologies. When I manually tested the oil pressure at the sensor it confirmed that I was losing all oil pressure at the top side. The issue was the lifter. I replaced lifters and did the AFM delete with new camshaft. All is right as rain.